Can’t V carve frets of a guitar fretboard

Hi guys!

I’ve been routing some cutting boards last days to get myself familiar with carbide create and motion. I’m running a shapeoko 3 XL and all is going well and I’m having a lot of fun.

Now I want to go into the real deal why I bought the monster: guitar building and inlay work.

I’m trying to scribe my frets of my fretboard with a V bit (60degr), but carbide tells me “empty toolpath”.
Weird because this worked with the cutting boards…

I want to scribe the middle line (which is the centre of my fret). Already tried to create an offset line around my fretboard and to select the outer two lines (contour of the fret), but it keeps giving me the same message…

Any professional help here? :joy:

I’m sorry for all the posts, but apparently as a new user I can’t upload all my photos in one post.

Thank you kindly for the help! :pray:

You can only use V carving w/ a closed toolpath.

That said, you can assign a V endmill to a polyline or curve and set it to cut at a desired depth:

which will afford more control and not result in the plunging at the ends of a V carve.

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Why scribe the lines when you can slot the fretboard with CNC. I’ve built over 30 guitars and sure would have done that if I’d had my machine then.

Aren’t fret slots very narrow and require a small (and expensive, and fragile) tool?

Around 0.025" (0.6 mm). So you’d need a 0.020" (0.5 mm) tool. & fretboards are usually some pretty hard wood, maple, ebony, etc… Around 0.060" deep. It could be done, but you’d have to really dainty with that little tool.


Fret slots are generally 0.020" to 0.025" wide for acoustic guitars although it varies per wire specs. For the inlay work I’ve posted on this site this is a fairly fat bit! I often use bits 0.178 mm in ebony.

The last wire I used, StewMac #152 recommended 0.023" (0.58 mm) slots. The tang on this wire is 0.062" (0.157 mm) deep. Rogue Systems, on Bay, has a bit measuring 0.508 mm diameter by 1.52 mm deep at a cost of $25/5 bits. Kyocera 1610-0210.063 measures 0.53 mm diameter by 1.60 mm deep costing $9.33 from drillman also on eBay. Both these would require a touch-up with a fret saw to increase depth especially on a radiused board. [prices may be dated!] BTW, these are both excellent sources of bits of fine inlay.

The caveat here is that I have not done this. Perhaps it’s more trouble than it’s worth especially with the slow cutting in ebony or maple. I had made a pretty nice jig for the hand sawing which would could have been used with the vee bit scoring but I wouldn’t have free cut the slots, I’m a bit to wobbly for that.


I’m certainly no luthier but I did build a guitar recently. Here’s a quote from that thread you might check out.

I’m now moving on to utilizing tools provided by Brad Anderson (referenced in a post above) in his YT channel . He has shared an excellent addin for Fusion 360 that will generate a neck and fretboard design after you have plugged in your desired values. (68.7 KB)

The guitar engine for Fusion is pretty cool, very flexible. Makes fret cutting a snap. Not to mention t.he entire design/cam process.


If one would like to mill the slot, Harvey Tool does carry a .020" diameter end mill that will reach .060" depth. Part number 998520. It is designed for plastic but should work fine in the harder woods. The .025" diameter (998525) will reach .075" deep but I’m afraid it will cut oversize due to run-out. In both cases, they have a 1/8" shank. One should always remove the tool collet from the spindle and clean both the collet and spindle taper to reduce run-out.


I use “Sparky” for fret slots, using 0.5mm bits from Amazon. Good results, but the bits are easy to break. I use Fusion360 these days, but started with Carbide Create. I’m away from my machine but can look up frets and speeds for you.


Look up Drillman on eBay. His .023 bits are perfect for fret slots. They are like $5 each or 5 for $15. I buy them 10 at a time. I have not broken one while cutting fretslots. Ever. I have only broken them from mishandling (hit the tip, drop etc). I also use them for cutting MOP for inlays.

For Brazilian rosewood or really any fretboard material, I use the standard 40% of cutter size for DOC. IE I am going something like …010” DOC at a time and federate of about 40 ipm. I use Fusion 360 and project the image on the radius fretboard so it cuts the slots in a radius as well. I go to a depth of about .070” as you will sand some of the radius to clean it up after the initial shaping. Then you can use your fret saw with depth stop to fine tune before fretting.


So this worked for me… I was trying to ‘v-carve’ the slot, and just pressing ‘contour’ with no offset should do the trick. The test fretboard came out pretty nice! Thanks for the tips (by now my motherboard is fried so I’m out of machine for a while…)


Thanks for the links! As soon as I’m ready to learn fusion 360, it’s the first thing I’ll do. But for now I’m only adept into machinery. Been building classical guitars and lutes by hand for over ten years now.
I’ll get there! :joy:


Please let us know about the motherboard issue at and we’ll do our best to assist.

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Thanks Will, I’ve sent a mail one hour ago. :crossed_fingers:

I made a harpejji clone over the pandemic and used my Shapeoko to cut fret slots that were about 8" long each (which is damn near impossible to do with a fret saw).

Here’s the bit I used. Broke several, but once I dialed in the speed and settings, they stopped breaking.

I went really really slow, something like 0.1 mm depth per pass, and the whole job tool maybe 6 hours. (In my case, I cut the depth of the center of the frets deeper than the fretwire is tall. This is because the instrument needs the frets to connect electrically to a wire that runs underneath and up to the circuit at the head of the instrument. After some failed solder experiments, I just threaded some wire strands up through a hole from the underside into the fret slot, and the “connection” is just the fretwire being pushed and held against the wire strands when I put the fret wire into the slots.)

Happy to elaborate if it’s helpful to anyone.

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